Optical storage systems such as DVD-RAM and DVD+RW offer the ability to store large amounts of digital information. Derived from earlier Compact Disc technology, information is stored along a single groove spiraling along the disc. For writeable and rewriteable systems, addressing information must be provided which allows the single long spiral to be divided into storage segments. In DVD+RW and DVD-RAM systems, disk address information may be encoded in missing pulses in a high frequency wobble signal placed along the recording groove.
Detecting these missing pulses in the high frequency wobble signal is made more difficult by crosstalk from other signals and noise inherent in the system, such as that introduced by the tracking process.
Address information encoded in a high frequency wobble signal in an optical storage subsystem is detected as missing pulses in the high frequency wobble signal using an homodyne synchronous detector. The input signal from an optical pickup is fed to a zonal bandpass filter then processed by a limiter. The input signal is also fed through a high pass filter to eliminate low frequency components. An analog multiplier forms the product of these two signals. The output of the analog multiplier is passed through low pass and high pass filters to remove noise, then passed to a threshold detector which outputs a signal indicating a missing wobble pulse.